Field of the Invention
The invention relates in general to an operating mode distinguishing method, a touch point locating method and a touch control circuit, and more particularly to an operating mode distinguishing method, a touch point locating method and a touch control circuit applied for underwater operations.
Description of the Related Art
As smart phones and tablet computers have become mainstream information products, touchpads that perform command input using touch control gestures have also become popular human-machine interface (HMI) control apparatuses among users.
FIG. 1a shows a sectional view of a conventional capacitive touchpad. As shown, a plurality of sensing electrodes 11 to 14 are disposed below a substrate 1, which is a cover lens made of glass, for example. When a finger 19 touches the top of the substrate 1, some of the sensing electrodes 11 to 14 are coupled to the finger 19 to generate changes in capacitance values. For example, a self capacitance CS3 of self capacitances CS1 to CS4 in the diagram has a change in the capacitance value due to the touch of the finger 19. The sensing electrodes 11 to 14 are then scanned by a touch control circuit (not shown) to detect changes in mutual capacitances CM1 to CM3 among the sensing electrodes 11 to 14 and/or the above self capacitances CS1 to SC4, hence further estimating the position of the finger 19.
The number of portable devices with a waterproof function is increasing. However, when a portable device including the abovementioned capacitive touchpad is operated under water, water 18 covering the top of the substrate 1 (as shown in FIG. 1b) may cause an effect similar to an entire hand pressing upon the capacitive touchpad, leading to an issue of incapable of effectively determining the touch position. Therefore, there is a need for a capacitive touchpad that is operable under water.